1. Field
The present disclosure generally relates to methods and apparatus for predicting a channel quality indicator (CQI) in a communication system, and more particularly to predicting a CQI for a receiver based on a function of different CQI values.
2. Background
Channel state estimation and feedback of the channel state estimation are essential components of current and future wireless systems, such as High Speed Downlink Packet Access (HSDPA), Evolution Data Only/Optimized (EVDO), Ultra Mobile Broadband (UMB), and other similar systems. In such systems, the receiver at a device estimates a Channel Quality Indicator (CQI), e.g., a Signal-to-Noise Ratio (SNR) of the channel, and feeds it back to the transmitter of the device for proper scheduling.
An emerging trend in wireless receivers, however, is to use advanced offline or delayed receivers, which store samples for a period of time and then process these stored samples in batches using an equalizer, interference cancellation receiver, or other similar receiver. This approach, however, introduces significant delay due to waiting that occurs for the batch data to arrive, and due to computing parameters of the receiver. In addition, delay is introduced due to the particular application of the receiver (i.e., equalizer filtering, or interference cancellation).
A fundamental issue that arises is that such processing delay causes the CQI of the delayed receiver fed back to the transmitter to become stale (i.e., not current). For example, if the receiver chain introduces a Δt time delay, then the reported CQI at a current time t+Δt would be based on channel conditions at previous time t. Stale CQI reporting degrades the CQI-based scheduling performance and makes passing conformance tests problematic.